Electromagnetic stepping device



MUM mrmmm QLU-LC KR 3 13%1 v 289 y 2, 1968 DANILEWICZ ET AL 3,391,289

ELECTROMAGNETIC STEPPING DEVICE 2 Sheets-Sheet 1 Filed March 16, 1965 y 2, 1968 L; DANILEWICZ ET AL 3,391,289

ELECTROMAGNETIC STEPPING DEVICE 2 Sheets-Sheet 2 Filed March 16, 1965 3,391,289 ELECTROMAGNETIC STEPPING DEVICE Ludomir Danilewicz, Wembley Park, and Leonard S.

Danilewicz, Ruislip, England, assignors to Plessey- UK Limited, Ilford, England, a British company Filed Mar. 16, 1965, Ser. No. 440.265 Claims priority, application Great Britain, Mar. 17, 1964,

I ,117/64 8 Claims. (Cl. 310--37) ABSTRACT OF THE DISCLOSURE An electromagnetic device in which a first armature is caused to oscillate by the successive energisation and deenergisation of an electromagnetic structure and in which a second armature, which is fixedly secured to an output member is magnetically coupled to the first armature to produce unidirectional stepped movement of the output member.

This invention relates to electromagnetic devices of the kind capable of transforming reciprocatory or oscillatory, movement into an interrupted unidirectional one. This movement may be linear or rotary.

According to the present invention there is provided an electromagnetic device of the kind specified comprising an electromagnet structure having pole-pieces and two associated armatures having teeth facing one another and arranged so that in response to successive energisations and de-energisations of the electromagnet structure and the simultaneous reciprocation or oscillation of a first of said armatures a second armature is caused to step unidirectionally.

The two armatures may be contained within a wide gap between the pole-pieces of the electromagnet structure and they may be movable inside the gap so that they complete the magnetic path without touching each of the pole-pieces of the electromagnetic structure. Both of the armatures may be provided with teeth of the same pitch.

If the electromagnet structure is energised the magnetic flux tends to be greatest when teeth of both armatures are aligned with each other and this relative position will therefore be forcibly maintained within the limits of magnetic attraction between the teeth. If the energising current is interrupted the flux collapses and the armatures are then free to move independently.

If the first armature is made to execute a reciprocating or oscillating movement roughly equal in length to one or more distances between its teeth, these will obviously face the teeth of the second armature in its outermost positions in the case of linear armatures. By arranging the electromagnet to be energised when the first armature moves in one particular direction and de-energised in the opposite direction, the second armature would be shifted by the force of magnetic attraction always in one direction. By leaving the current to flow continuously reciprocatory or oscillatory movement could be transmitted from the first armature to the second.

It' is not essential to drive the first armature externally since it may be arranged that it tends to occupy an asymmetrical position with respect to the pole-pieces when the electromagnet is de-energised and it will be forced by the magnetic flux to assume a central position between the pole-pieces when the current is switched on. This reciprocaitng or oscillating movement may be achieved by providing two limit stops and a return spring. The second armature would follow the first one only when the electromagnet is energised. When the current is otf the first armature returns alone. 1

Some suitable indexing device may be arranged to hold nited States Patent "ice enemas; Patented July 2, 19fi8 the second armature when the first one is returning. This device can be of any conventional form but it could be made so that the magnetic flux actuates it to render it ineffectual when the second armature is about to move thus making its registering action more positive. Of course a separate electromagnet energised simultaneously with the main one can be made to lift the indexing device.

By way of example reference will now be made to the accompanying drawings in which;

FIG. 1 is a diagrammatic view of an electromagnetic device for affording linear unidirectional movement of an armature in response to externally applied reciprocating drive to the other armature of the device;

FIG. 2 is a view similar to that shown in FIG. 1 for internally generated reciprocating movement of the reciprocating armature;

FIGS. 3 and 4 show diagrammatic views of alternative devices according to the invention for producing rotary unidirectional movement of an armature.

FIG. 5 is a diagrammatic view of an electromagnetic detent arrangement for the unidirectional armature of devices according to FIGS. 1 and 2;

FIG. 6 is a diagrammatic view of a device in which the oscillating and unidirectional armatures have different numbers of teeth;

FIG. 7 is a cut-away perspective view of another form of rotary electromagnetic device according to the invention; and

FIG. 8 is a fragmentary view of the device according to FIG. 4 in which a tapered air gap between the teeth of the two armatures is provided.

Referring to FIG. 1, there is shown an electromagnetic device for converting reciprocatory linear movement into interrupted unidirectional movement. The device comprises an electromagnet 1 having pole-pieces designated N and S, respectively, defining between them a wide air gap 2. In this air gap are arranged two armatures 3 and 4 of magnetic material having teeth 5 and 6 which face one another as shown. The armature 4 is arranged to be reciprocated in the directions indicated. With the electromagnet 1 energised to produce the poles as shown in the electromagnet poles are induced in the teeth of the armatures 3 and 4 as indicated. If the reciprocating armature 4 is moved to the right then the teeth of the armature 4 become mis-aligned with those of the armature 3 and the latter accordingly moves to the right in order to take up a position at which the low reluctance path is established across the teeth 5 and 6 by again becoming directly aligned as shown in the drawing. If at the end of its stroke the electromagnet is de-energised the armature 4 is de-magnetised and can then be moved back to its former position without affecting the position of armature 3. Thus by successive energisations and de-energisations of the electromagnet the armature 3 can he stepped to the right.

Referring to FIG. 2, this shows an arrangement for internally produced reciprocation of the armature 4 to produce unidirectional stepping movement of the armature 3. The armature 4 is biased against a stop 7 by a tension spring 8. When the electromagnet 1 is energised, the armature 4 is attracted between the poles N and S of the magnet 1. As it moves to the right and eventually bears against stop 9, the armature 3 follows suit. Upon de-ener gisation of the magnet 1 the spring 8 restores the armature 4 to its former position, as shown, but the position of armature 3 remains unchanged.

In FIGS. 3 and 4 there are shown two rotary devices embodying the principle of the present invention. The electromagnet structure of these devices hasa cup-shaped core with a cylindrical wall 10 in FIG. 3, which may have cut-away portions to define teeth 11, as shown in FIG. 4. The core also includes a central spigot piece 12.

The annular space defined between the pole-pieces of the core accommodates two concentric armatures 13 and 14 in FIG. 3. The outer armature 13 is arranged to be oscillated by external means (not shown) so that the inner armature 14 is rotated stepwise in the direction indicated responsively to successive energisations of the electromagnet.

The arrangement of FIG. 4 by providing the teeth 11 enables the armature 15 having tooth portions 16 to be self oscillated by providing a biasing spring and stop means (not shown) but corresponding generally to the parts 7, 8 and 9 in FIG. 2.

It will be appreciated that movement of the reciprocating or oscillating armature, such as the armature 4 of FIGS. 1 and 2, when the electromagnet 1 is de-energised does not influence the position of the unidirectional armature, but positively to prevent any wander of the undirectional armature electromagnetic detent means may be provided as shown in FIG. 5. The detent means comprises a spring-urged member 17 having a detent 18 which, when the electromagnet 1 is de-energised, engages with a notch 19 in the armature 3 but which is withdrawn to permit follower movement of the armature 3 when the electromagnet is energised, by the attraction of the head 20 to the pole 21 of the electromagnet.

Turning now to FIG. 6, this shows an alternative arrangement to FIG. 4 in which the unidirectional armature 22 and the oscillating armature 23 have difierent numbers of teeth and different pitches. The principle of operation is nevertheless the same, affording internal reciprocating action of the armature 23.

FIG. 7 shows in greater detail yet another embodiment of a rotary device in which the electromagnet has self supporting Winding 24 surrounding but not engaging with an oscillating armature 25 having two toothed sections 26 and 27 joined by a bored cylindrical piece 28. The teeth of the section 26 co-operate with teeth 29 on the cylindrical core pole-piece 30 while the teeth of the armature section 27 co-operate with teeth 31 on a unidirectional armature 32 which is secured to a non-magnetic plate 33 fixedly attached to an output shaft 34. The armature 25 is shown in the position at the end of a stroke upon the electromagnet having been energised, as is the case of FIG. 6. When the electro-magnet winding 24 is rte-energised the armature 25 will be returned through a small angle by a helical return spring 36, the ends of which abut a pin 37 on the armature 25 and a pin 38 secured to the outer casing such that the armature 25 is biased in an anti-clockwise direction (as viewed in the drawing), with respect to the outer casing, the movement of the armature 25 being determined by pin 37 engaging with a slot (not shown) in the end. plate of the outer casing so that the teeth of the section 26 become mis-aligned with the teeth 29. The unidirectionl armature 31 may be held by a detent or indexing arrangement (not shown). When the electromagnet 24 is re-energised the teeth 29 tend to re-align with the teeth on section 26 and the teeth on the member 31 tend to move into align ment with the teeth on the armature section 27 thus bringing about unidirectional stepwise rotation of the armature 31 and the output shaft 34.

Referring to FIG. 8, this shows a fragment of the FIG. 4 construction but with a tapered air gap between teeth of the armature 16 and teeth 11 of the electromagnet. This gap is arranged to decrease in width in response to clockwise rotation of the armature 16 by 4 providing eccentric co-opcrating surfaces on the pole teeth.

What we claim is:

1. An electromagnetic unidirectional stepping device for providing unidirectional, stepped rotary movement of an output member comprising an electromagnetic structure, a first armature operatively associated with said electromagnetic structure for effecting rotary movement of said armature from a rest position in response to energisation of the electromagnetic structure, restoring means for returning the first armature to the rest position upon deenergisntion of the electromagnetic structure, a second armature carried on the output member, the second armature being magnetically coupled without physical contact with the first armature during energisation only of the electromagnetic structure and thereby rotated unidirectionally in response to rotary movement of the first armature.

2. An electromagnetic device according to claim 1, in which the electromagnetic structure comprises a toothed core, and in which the first armature has teeth which are mis-aligned with the teeth of the toothed core in the tie-energised state of the electromagnetic structure.

3. An electromagnetic device according to claim 2, in which the teeth of the toothed core and the teeth of the first armature define between them tapered air gaps, the width of which decreases in response to movement of the first armature from the rest position.

4. An electromagnetic device according to claim 1, having indexing means for restraining the second armature against reverse :movement.

5. An electromagnetic device according to claim 4, in which the indexing means is electromagnetically actuated to permit movement of the second armature when the electromagnetic structure is energised.

6. An electromagnetic device according to claim 5, in which the indexing means comprises detent means and is actuated by said electromagnetic structure.

7. An electromagnetic device according to claim 1, in which the electromagnetic structure comprises a cupshaped core having a cylindrical wall portion and a central core portion which between them define an annular gap which accommodates two generally concentric armature structures.

8. An electromagnetic device according to claim 7, in which the first armature comprises two spaced apart, interconnected toothed discs, the teeth of one toothed disc co-operating with teeth on the electromagnetic core structure and the teeth of the other toothed disc co-operating with teeth of the second armature, which comprises a toothed disc fixedly secured to an output shaft, for producing unidirectional stepwise rotation of the output mem ber.

References Cited UNITED STATES PATENTS 3,159,759 12/1964 Conrad et a1. 310-103 XR 3,293,580 12/1966 Cotton 310-49 XR 1,422,243 7/1922 Van Norden 310-103 1,640,742 8/1927 Wallace et al. 310-34 2,475,232 7/1949 Gianini 310-37 X 3,162,796 12/1964 Schreiber et a1. 310-12 X MILTON O. HIRSHFIELD, Primary Examiner.

D. F. DUGGAN, Assistant Examiner. 

